Method for receiving beam recovery request and network device

ABSTRACT

The present disclosure relates to methods for sending a message. One example method is applied to a terminal device and includes sending a request sequence to a network device, receiving a response message sent by the network device, where the response message indicates a time-frequency resource that the network device allocates to the terminal device in response to the request sequence, and sending an indication message to the network device on the time-frequency resource, where the indication message indicates that the request sequence is used for at least one of the following: requesting beam recovery, requesting data scheduling, and requesting beam adjustment.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2018/085113, filed on Apr. 28, 2018 which claims priority toChinese Patent Application No. 201710312732.8, filed on May 5, 2017. Thedisclosures of the aforementioned applications are hereby incorporatedby reference in their entireties.

TECHNICAL FIELD

The present invention relates to the field of communicationstechnologies, and in particular, to a method for receiving a beamrecovery request and a network device.

BACKGROUND

To satisfy continuously growing communications service requirements,mobile communications systems are developing, for example, spectrumefficiency is improved, to resolve a problem of spectrum resourceshortage in an existing mobile communications system. However, spectrumefficiency improvement alone is insufficient to satisfy the continuouslygrowing communications service requirements.

The foregoing problem can be resolved by using a high frequency band.Deploying, in a high frequency band with a carrier frequency greaterthan 6 GHz, a 5th generation (5G) mobile communications system that isbeing standardized is being considered. The high frequency band includesa large quantity of available frequency resources. This can resolve theproblem of frequency shortage in the existing mobile communicationssystem, thereby greatly increasing a system capacity. However, in thehigh frequency band, a path loss of a signal increases greatly, andtherefore it is necessary to find a method for increasing receivedsignal power.

FIG. 1 is a schematic diagram of sending signals. As shown in FIG. 1,when a low frequency band or an intermediate frequency band is used,signals may be sent in all directions in a space or at a relatively wideangle; when a high frequency band is used, in virtue of a relativelysmall carrier wavelength of a high frequency communications system,antenna arrays including a large quantity of antenna elements may bedisposed at a transmit end and a receive end. The transmit end sendssignals by using a specific beamforming weight, so that the sent signalsform a beam with a spatial directivity, and the receive end receives thesignals through an antenna array by using a specific beamforming weight.In this way, receive power of the signals at the receive end can beimproved, to reduce a path loss.

SUMMARY

When a network device communicates with a terminal device by using abeam, because the terminal device moves or rotates or an environmentchanges, the terminal device may detect a beam failure. In this case,the terminal device initiates a beam recovery request to the networkdevice. However, when the network device communicates with the terminaldevice by using a beam obtained after adjustment, the terminal devicecannot learn of a time-frequency resource for initiating the beamrecovery request to the network device.

To resolve the foregoing technical problem, according to a first aspect,an embodiment of this application provides a method for receiving a beamrecovery request. The method is applied to a network device andincludes: sending a first signal to a terminal device by using a firstbeam; receiving first index information sent by the terminal device,where the first index information indicates an index number of the firstsignal; sending a first notification message to the terminal devicebased on the first index information, where the first notificationmessage includes second index information, the second index informationindicates an index number of a second signal, and the index number ofthe second signal corresponds to the first beam; and receiving, on atime-frequency resource corresponding to the first beam, the beamrecovery request sent by the terminal device. In this embodiment of thisapplication, after beam adjustment, the network device sends thenotification message to the terminal device to notify the terminaldevice of the index number of the periodic sweep beam obtained afteradjustment. After receiving the notification message, the terminaldevice can determine the index number of the periodic sweep beam alignedwith a beam used to initiate the beam recovery request, and furtherdetermine the time-frequency resource corresponding to the periodicsweep beam, so as to send a request sequence on the correcttime-frequency resource. In this way, the network device can correctlyreceive the beam recovery request initiated by the terminal device.

With reference to the first aspect, in a possible implementation, beforethe sending a first signal to a terminal device by using a first beam,the method further includes: sending the second signal to the terminaldevice by using the first beam; and receiving third index informationsent by the terminal device, where the third index information indicatesthe index number of the second signal.

With reference to the first aspect and all implementations of the firstaspect, in a possible implementation, after the sending a firstnotification message to the terminal device, the method furtherincludes: sending a third signal to the terminal device by using asecond beam; receiving fourth index information sent by the terminaldevice, where the fourth index information indicates an index number ofthe third signal; and sending a second notification message to theterminal device based on the fourth index information, where the secondnotification message includes fifth index information, the fifth indexinformation indicates a difference between an index number of a fourthsignal and the index number of the second signal, and the index numberof the fourth signal corresponds to the second beam. In this embodimentof this application, after beam adjustment, the network device sends thenotification message to the terminal device to notify the terminaldevice of the difference between the index number of the periodic sweepbeam obtained after adjustment and the index number, of the periodicsweep beam used before adjustment, in the previous notification message.This can save downlink signaling resources compared with notifying theterminal device of the index number of the periodic sweep beam obtainedafter adjustment.

With reference to the first aspect and all the implementations of thefirst aspect, in an implementation, that the second index informationindicates an index number of a second signal includes: the second indexinformation indicates that the first signal and the second signal arequasi co-located.

With reference to the first aspect and all the implementations of thefirst aspect, in an implementation, the first signal includes a firstchannel state information-reference signal CSI-RS, the second signalincludes a second CSI-RS or a first synchronization signal block SSblock, the third signal includes a third CSI-RS, and the fourth signalincludes a fourth CSI-RS or a second SS block.

According to a second aspect, an embodiment of this application providesa method for sending a message. The method is applied to a terminaldevice and includes: sending a request sequence to a network device;receiving a response message sent by the network device, where theresponse message indicates a time-frequency resource that the networkdevice allocates to the terminal device in response to the requestsequence; and sending an indication message to the network device on thetime-frequency resource, where the indication message indicates that therequest sequence is used for at least one of the following: requestingbeam recovery, requesting data scheduling, and requesting beamadjustment. In this embodiment of this application, the request sequencesent by the terminal device to the network device is not necessarilyused for requesting beam recovery, but may be reused for requesting beamadjustment and/or requesting data scheduling. The network deviceallocates the time-frequency resource to the terminal device in responseto the request sequence. The terminal device sends the indicationmessage to the network device on the allocated time-frequency resource,and indicates an actual function of the request sequence in theindication message. The request sequence is reused for several possiblerequests, so that a large quantity of sequence resources are saved.

With reference to the second aspect and all implementations of thesecond aspect, in an implementation, when the request sequence is usedat least for requesting beam recovery, the indication message furtherincludes at least one of the following: a beam failure cause, a quantityof failed beams, a beam failure status, an index number of an availablebeam, and quality of the available beam. In this embodiment of thisapplication, the indication message not only indicates the actualfunction of the request sequence, but also indicates auxiliaryinformation. This further saves signaling resources.

With reference to the second aspect and all the implementations of thesecond aspect, in an implementation, the quantity of failed beams isindicated by using a field of the quantity of failed beams; and that thefield of the quantity of failed beams is 00, 01, 10, or 11 indicatesthat the quantity of failed beams is 1, 2, 3, or 4, respectively.

With reference to the second aspect and all the implementations of thesecond aspect, in an implementation, the beam failure status isindicated by using a field of the beam failure status; and that thefield of the beam failure status is 00 or 01 indicates that the beamfailure status is that a current serving beam fails or all serving beamsfail, respectively.

With reference to the second aspect and all the implementations of thesecond aspect, in an implementation, when the request sequence is usedat least for requesting beam recovery, before the sending a requestsequence to a network device, the method further includes: receiving afirst signal sent by the network device by using a first beam; anddetecting that a received signal strength of the first signal is lessthan or equal to a first preset threshold.

With reference to the second aspect and all the implementations of thesecond aspect, in an implementation, after the detecting that a receivedsignal strength of the first signal is less than or equal to a firstpreset threshold, the method further includes: receiving a second signalsent by the network device by using a second beam; detecting that areceived signal strength of the second signal is greater than or equalto a second preset threshold; and sending first index information to thenetwork device, where the first index information indicates an indexnumber of the second signal. In this embodiment of this application,when the terminal device detects a beam failure, the terminal devicefurther needs to detect existence of an available beam before initiatinga beam recovery request to the network device. This can avoid a waste ofsignaling resources that is caused when there is no available beam afterthe terminal device initiates the beam recovery request.

With reference to the second aspect and all the implementations of thesecond aspect, in an implementation, when the request sequence is usedat least for requesting data scheduling, the indication message furtherincludes a buffer status report BSR. In this embodiment of thisapplication, the indication message not only indicates the actualfunction of the request sequence, but also indicates auxiliaryinformation. This further saves signaling resources.

With reference to the second aspect and all the implementations of thesecond aspect, in an implementation, after the sending a requestsequence to a network device, the method further includes: if theresponse message is not received within a preset time, resending therequest sequence to the network device; and when a quantity of times ofsending the request sequence to the network device reaches a presetmaximum quantity of sending times, performing one of the following:initiating a random access process, reporting a beam recovery failure,and reporting a radio link failure.

With reference to the second aspect and all the implementations of thesecond aspect, in an implementation, the response message is scrambledby using a radio network temporary identifier RNTI, and the RNTI isobtained by using a preset function and at least one of the followingvariables: an index number of the request sequence, an index number of atime resource for sending the request sequence, and an index number of afrequency resource for sending the request sequence. In this embodimentof this application, there is a specific probability that the networkdevice incorrectly determines which terminal device sends the requestsequence, and a terminal device that does not send the request sequencealso decodes the response message after receiving the response message.To avoid this case, the network device may scramble the response messageby using the RNTI. In this way, once detecting the RNTI after receivingthe response message, the terminal device that does not send the requestsequence does not decode the response message.

With reference to the second aspect and all the implementations of thesecond aspect, in an implementation, the indication message is carriedby at least one media access control control element MAC CE.

According to a third aspect, an embodiment of this application providesa network device, including: a transceiver; a memory, configured tostore program code including a computer operation instruction; and aprocessor, configured to execute the computer operation instruction, tocontrol the transceiver to perform the following operations: receivingfirst index information sent by a terminal device, where the first indexinformation indicates an index number of a first signal; sending a firstnotification message to the terminal device based on the first indexinformation, where the first notification message includes second indexinformation, the second index information indicates an index number of asecond signal, and the index number of the second signal corresponds toa first beam; and receiving, on a time-frequency resource correspondingto the first beam, a beam recovery request sent by the terminal device.

With reference to the third aspect and all implementations of the thirdaspect, in an implementation, the processor is further configured tocontrol the transceiver to perform the following operations: sending thesecond signal to the terminal device by using the first beam; andreceiving third index information sent by the terminal device, where thethird index information indicates the index number of the second signal.

With reference to the third aspect and all the implementations of thethird aspect, in an implementation, the processor is further configuredto control the transceiver to perform the following operations: sendinga third signal to the terminal device by using a second beam; receivingfourth index information sent by the terminal device, where the fourthindex information indicates an index number of the third signal; andsending a second notification message to the terminal device based onthe fourth index information, where the second notification messageincludes fifth index information, the fifth index information indicatesa difference between an index number of a fourth signal and the indexnumber of the second signal, and the index number of the fourth signalcorresponds to the second beam.

With reference to the third aspect and all the implementations of thethird aspect, in an implementation, that the second index informationindicates an index number of a second signal includes: the second indexinformation indicates that the first signal and the second signal arequasi co-located.

With reference to the third aspect and all the implementations of thethird aspect, in an implementation, the first signal includes a firstchannel state information-reference signal CSI-RS, the second signalincludes a second CSI-RS or a first synchronization signal block SSblock, the third signal includes a third CSI-RS, and the fourth signalincludes a fourth CSI-RS or a second SS block.

According to a fourth aspect, an embodiment of this application providesa terminal device, including: a transceiver; a memory, configured tostore program code including a computer operation instruction; and aprocessor, configured to execute the computer operation instruction, tocontrol the transceiver to perform the following operations: sending arequest sequence to a network device; receiving a response message sentby the network device, where the response message indicates atime-frequency resource that the network device allocates to theterminal device in response to the request sequence; and sending anindication message to the network device on the time-frequency resource,where the indication message indicates that the request sequence is usedfor at least one of the following: requesting beam recovery, requestingdata scheduling, and requesting beam adjustment.

With reference to the fourth aspect and all implementations of thefourth aspect, in an implementation, when the request sequence is usedat least for requesting beam recovery, the indication message furtherincludes at least one of the following: a beam failure cause, a quantityof failed beams, a beam failure status, an index number of an availablebeam, and quality of the available beam.

With reference to the fourth aspect and all the implementations of thefourth aspect, in an implementation, the quantity of failed beams isindicated by using a field of the quantity of failed beams; and that thefield of the quantity of failed beams is 00, 01, 10, or 11 indicatesthat the quantity of failed beams is 1, 2, 3, or 4, respectively.

With reference to the fourth aspect and all the implementations of thefourth aspect, in an implementation, the beam failure status isindicated by using a field of the beam failure status; and that thefield of the beam failure status is 00 or 01 indicates that the beamfailure status is that a current serving beam fails or all serving beamsfail, respectively.

With reference to the fourth aspect and all the implementations of thefourth aspect, in an implementation, when the request sequence is usedat least for requesting beam recovery, the processor is furtherconfigured to control the transceiver to perform the followingoperations: receiving a first signal sent by the network device by usinga first beam; and detecting that a received signal strength of the firstsignal is less than or equal to a first preset threshold.

With reference to the fourth aspect and all the implementations of thefourth aspect, in an implementation, the processor is further configuredto control the transceiver to perform the following operations:

receiving a second signal sent by the network device by using a secondbeam; detecting that a received signal strength of the second signal isgreater than or equal to a second preset threshold; and sending firstindex information to the network device, where the first indexinformation indicates an index number of the second signal.

With reference to the fourth aspect and all the implementations of thefourth aspect, in an implementation, when the request sequence is usedat least for requesting data scheduling, the indication message furtherincludes a buffer status report BSR.

With reference to the fourth aspect and all the implementations of thefourth aspect, in an implementation, the processor is further configuredto control the transceiver to perform the following operations: if theresponse message is not received within a preset time, resending therequest sequence to the network device; and when a quantity of times ofsending the request sequence to the network device reaches a presetmaximum quantity of sending times, performing one of the following:initiating a random access process, reporting a beam recovery failure,and reporting a radio link failure.

With reference to the fourth aspect and all the implementations of thefourth aspect, in an implementation, the response message is scrambledby using a radio network temporary identifier RNTI, and the RNTI isobtained by using a preset function and at least one of the followingvariables: an index number of the request sequence, an index number of atime resource for sending the request sequence, and an index number of afrequency resource for sending the request sequence.

With reference to the fourth aspect and all the implementations of thefourth aspect, in an implementation, the indication message is carriedby at least one media access control control element MAC CE.

According to a fifth aspect, an embodiment of this application providesa method for sending a beam recovery request, including: sending arequest sequence to a network device; receiving a response message sentby the network device, where the response message indicates that thenetwork device responds to the request sequence; and sending anindication message to the network device, where the indication messageindicates that the request sequence is used for at least one of thefollowing: requesting beam recovery, requesting data scheduling, andrequesting beam adjustment. In this embodiment of this application, therequest sequence sent by the terminal device to the network device isnot necessarily used for requesting beam recovery, but may be reused forrequesting beam adjustment and/or requesting data scheduling.

Another aspect of embodiments of this application provides a computerprogram product that includes an instruction. When the instruction runson a computer, the computer is enabled to perform the method in theforegoing aspects.

Still another aspect of the embodiments of this application provides acommunications chip that stores an instruction. When the instructionruns on a network device or a terminal device, the network device or theterminal device is enabled to perform the method in the foregoingaspects.

Yet another aspect of the embodiments of this application provides acomputer readable storage medium. The computer readable storage mediumstores an instruction. When the instruction runs on a computer, thecomputer is enabled to perform the method in the foregoing aspects.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of sending signals;

FIG. 2 is a schematic diagram of an application scenario of a technicalsolution according to an embodiment of this application;

FIG. 3 is a schematic diagram of a general hardware architecture of abase station according to an embodiment of this application;

FIG. 4 is a schematic diagram of a general hardware architecture of amobile phone according to an embodiment of this application;

FIG. 5 is a schematic flowchart of a method for communication between anetwork device and a terminal device by using a beam pair according toan embodiment of this application;

FIG. 6 is a schematic diagram of periodic beam sweeping performed by anetwork device;

FIG. 7 is a schematic diagram of beam adjustment according to anembodiment of this application;

FIG. 8 is a schematic diagram of sending a request sequence on atime-frequency resource without beam adjustment according to anembodiment of this application;

FIG. 9 is a schematic diagram of sending a request sequence on atime-frequency resource after beam adjustment according to an embodimentof this application;

FIG. 10 is a schematic flowchart of a method for sending a messageaccording to an embodiment of this application;

FIG. 11 is a schematic diagram of an indication message according to anembodiment of this application;

FIG. 12 is a schematic structural diagram of a network device accordingto an embodiment of this application;

FIG. 13 is a schematic apparatus diagram of a terminal device accordingto an embodiment of this application;

FIG. 14 is a schematic apparatus diagram of another network deviceaccording to an embodiment of this application; and

FIG. 15 is a schematic apparatus diagram of another terminal deviceaccording to an embodiment of this application.

DESCRIPTION OF EMBODIMENTS

For ease of understanding, before embodiments of this application aredescribed, related technologies and related terms in the embodiments ofthis application are first introduced briefly.

Beamforming (beamforming): Beamforming may also be referred to asspatial filtering, and is a signal processing technology in whichsignals are directionally sent and received by using an antenna array.In beamforming, a beamforming weight of an antenna array is set, so thatsignals at some angles are constructively interfered and signals atother angles are destructively interfered. Beamforming can be used forsending a signal at a transmit end, and can also be used for receiving asignal at a receive end.

Transmit beamforming: When a transmit end with an antenna array sends asignal, a specific amplitude and phase are set on each antenna elementin the antenna array, so that the sent signal has a specific spatialdirectivity, to be specific, signal power in some directions is high,signal power in some directions is low, and a direction with highestsignal power is a direction of a transmit beam. The antenna arrayincludes a plurality of antenna elements. The additional specificamplitude and phase are a beamforming weight.

Transmit beam: A transmit beam is a beam that has a spatial directivityand that is formed by a signal sent by a transmit end by using aspecific beamforming weight.

Receive beamforming: When a receive end with an antenna array receives asignal, a specific amplitude and phase are set on each antenna elementin the antenna array, so that a power gain of the received signal has adirectivity, to be specific, power gains of signals received in somedirections are high, power gains of signals received in some directionsare low, and a direction with a highest power gain in signal receptionis a direction of a receive beam. The antenna array includes a pluralityof antenna elements. The additional specific amplitude and phase are abeamforming weight.

Receive beam: A receive beam is a beam that has a spatial directivityand that is formed by a signal received by a receive end by using aspecific beamforming weight.

Sending a signal by using a transmit beam means sending the signal byusing a beamforming weight.

Receiving a signal by using a receive beam means receiving the signal byusing a beamforming weight.

Beam pair (beam pair): One beam pair includes one transmit beam and onereceive beam. Beam pairs may be further classified into an uplink beampair and a downlink beam pair. The downlink beam pair refers to atransmit beam of a network device and a receive beam of a terminaldevice. The uplink beam pair refers to a transmit beam of a terminaldevice and a receive beam of a network device.

Beam alignment: A transmit end sends signals to a receive end by usingdifferent transmit beams. The receive end receives, by using a specificreceive beam, the signals sent by the transmit end, and measures signalgains of the received signals. When a signal gain of a signal sent byusing one of the transmit beams is greater than a preset threshold, beamalignment is implemented between the transmit beam and the specificreceive beam that is used by the receive end, in other words, thetransmit beam is aligned with the specific receive beam used by thereceive end.

Beam correspondence (beam correspondence): A transmit beam and a receivebeam between which beam alignment is implemented have a beamcorrespondence. To be specific, it is assumed that in downlinkcommunication, a transmit beam of a network device is a beam A, areceive beam of a terminal device is a beam B, and the beam A is alignedwith and the beam B; in this case, in uplink communication, the terminaldevice uses the beam B as a transmit beam, and the network device usesthe beam A as a receive beam. A beam correspondence can also indicatethat the beam B is aligned with the beam A.

The following describes application scenarios and devices of technicalsolutions in the embodiments of this application with reference toaccompanying drawings.

FIG. 2 is a schematic diagram of an application scenario of a technicalsolution according to an embodiment of this application. As shown inFIG. 2, a network device has six different transmit beams B1 to B6 on aradio frequency channel, and uses different transmit beamforming for thesix beams. As a receive end of the radio frequency channel, a terminaldevice 1 has one beam A1. As a receive end of the radio frequencychannel, a terminal device 2 has two beams: A1 and A2. Beam pairinformation is established between the network device and the terminaldevice 1 by using B1 to B4 and A1, for communication between the networkdevice and the terminal device 1. Beam pair information is establishedbetween the network device and the terminal device 2 by using B3 to B6,A1 and A2, for communication between the network device and the terminaldevice 2. It should be understood that this application is applied toany beamforming-based communication between a network device and aterminal device. FIG. 2 only shows a scenario in which the networkdevice serves as a transmit end and the terminal device serves as thereceive end in downlink communication. However, in uplink communication,the terminal device may also serve as a transmit end, and the networkdevice serves as a receive end.

The network device may be a device capable of communicating with theterminal device. The network device may be a base station, a relaystation, an access point, or the like. The base station may be a basetransceiver station (base transceiver station, BTS for short) in aglobal system for mobile communications (global system for mobilecommunications, GSM for short) or code division multiple access (codedivision multiple access, CDMA for short) network; may be an NB (NodeB)in wideband code division multiple access (wideband code divisionmultiple access, WCDMA for short); or may be an eNB or eNodeB (evolvedNodeB) in LTE. The network device may be alternatively a radiocontroller in a cloud radio access network (cloud radio access network,CRAN for short) scenario. The network device may be alternatively anetwork device in a future 5G network or a network device in a futureevolved PLMN, or may be a wearable device, a vehicle-mounted device, orthe like.

The terminal device 1 or the terminal device 2 may be UE, an accessterminal, a UE unit, a UE station, a mobile station, a mobile console, aremote station, a remote terminal, a mobile device, a UE terminal, aterminal, a wireless communications device, a UE agent, a UE apparatus,or the like. The access terminal may be a cellular phone, a cordlessphone, a session initiation protocol (session initiation protocol, SIPfor short) phone, a wireless local loop (wireless local loop, WLL forshort) station, a personal digital assistant (personal digitalassistant, PDA for short), a handheld device having a wirelesscommunication function, a computing device, another processing deviceconnected to a wireless modem, a vehicle-mounted device, a wearabledevice, a terminal device in the future 5G network, a terminal device inthe future evolved PLMN network, or the like.

It should be noted that this specification provides descriptions byusing examples in which a network device 100 is a base station and aterminal device 200 is UE.

An example in which the network device 100 is the base station is usedto describe a general hardware architecture of the base station. FIG. 3is a schematic diagram of a general hardware architecture of a basestation according to an embodiment of this application. As shown in FIG.3, the base station may include a building baseband unit (buildingbaseband unit, BBU for short) and a remote radio unit (remote radiounit, RRU for short). The RRU is connected to at least one antennasystem (namely, an antenna). The BBU and the RRU may be separated foruse, depending on a requirement.

An example in which the terminal device 200 is a mobile phone is used todescribe a general hardware architecture of the mobile phone. FIG. 4 isa schematic diagram of a general hardware architecture of a mobile phoneaccording to an embodiment of this application. As shown in FIG. 4, themobile phone may include components such as a radio frequency (RadioFrequency, RF) circuit 110, a memory 120, another input device 130, adisplay 140, a sensor 150, an audio circuit 160, an I/O subsystem 170, aprocessor 180, and a power supply 190. A person skilled in the art canunderstand that a structure of the mobile phone shown in FIG. 4 does notconstitute any limitation on the mobile phone. The mobile phone mayinclude more or fewer components than those shown in the figure, or somecomponents may be combined, or some components may be split, or thecomponents may be disposed differently. A person skilled in the art canunderstand that the display 140 belongs to a user interface (userInterface, UI) and the display 140 may include a display panel 141 and atouch panel 142. Although not shown, the mobile phone may furtherinclude function modules or components such as a camera and a Bluetoothmodule. Details are not described herein.

Further, the processor 180 is connected to each of the RF circuit 110,the memory 120, the audio circuit 160, the I/O subsystem 170, and thepower supply 190. The I/O subsystem 170 is connected to each of theanother input device 130, the display 140, and the sensor 150. The RFcircuit 110 may be configured to receive and send a signal in receivinga message and sending a message or during a call. In particular, afterreceiving downlink information of a base station, the RF circuit 110transfers the downlink information to the processor 180 for processing.The memory 120 may be configured to store program code that includes acomputer operation instruction. The processor 180 performs variousfunction applications and data processing of the mobile phone by runningthe program code stored in the memory 120. The another input device 130may be configured to receive input digital or character information, andgenerate a key signal input related to user settings and functioncontrol of the mobile phone. The display 140 may be configured todisplay information input by a user or information provided to a user,and various mobile phone menus, and may further accept user input. Thesensor 150 may be a light sensor, a motion sensor, or another sensor.The audio circuit 160 may provide an audio interface between the userand the mobile phone. The I/O subsystem 170 is configured to control aninput/output external device, and the external device may includeanother device input controller, a sensor controller, and a displaycontroller. The processor 180 is a control center of the mobile phone200, is connected to all parts of the entire mobile phone by usingvarious interfaces and lines, and performs various functions of themobile phone 200 and processes data by running or executing the programcode stored in the memory 120 and by invoking data stored in the memory120, to perform overall monitoring on the mobile phone. The power supply190 (such as a battery) is configured to supply power to the foregoingcomponents. Preferably, the power supply may be logically connected tothe processor 180 by using a power management system, to implementfunctions such as charge management, discharge management, and powerconsumption management by using the power management system.

The following describes the technical solutions in the embodiments ofthis application with reference to the accompanying drawings.

FIG. 5 is a schematic flowchart of a method for communication between anetwork device and a terminal device by using a beam pair according toan embodiment of this application. As shown in FIG. 5, the methodincludes the following steps.

S51: The network device and the terminal device establish a beam pairset that can be used for communication.

The network device and the terminal device may establish the beam pairset by performing the following steps.

S511: The network device performs periodic beam sweeping.

FIG. 6 is a schematic diagram of periodic beam sweeping performed by thenetwork device. As shown in FIG. 6, that the network device performsperiodic beam sweeping means that the network device periodically sendsN periodic sweep signals respectively by using N transmit beams(referred to as periodic sweep beams below). Types of periodic sweepsignals may include a synchronization signal block (synchronizationsignal block, SS Block for short) and a channel stateinformation-reference signal (channel state information-referencesignal, CSI-RS for short), and N is a positive integer. The networkdevice may alternatively send periodic sweep signals in a differentsweep period by using a different quantity of periodic sweep beams.

The N periodic sweep signals are in one-to-one correspondence with the Nperiodic sweep beams, and each of the N periodic sweep signals has anindex number. Both the network device and the terminal device candetermine, based on an index number of a periodic sweep signal, aperiodic sweep beam corresponding to the periodic sweep signal. An indexnumber of a periodic sweep signal is an index number of a periodic sweepbeam corresponding to the periodic sweep signal. For example, thenetwork device respectively sends, by using periodic sweep beams whosenumbers are 1 to 10, periodic sweep signals whose index numbers are 1 to10. In this case, the terminal device can determine, based on a periodicsweep signal whose index number is 5, a periodic sweep beam whose numberis 5.

An index number of an SS block may be a natural code (for example, apositive integer such as 1, 2, or 3), or may be represented by using atleast one of the following: a frame index number, a subframe indexnumber, a slot index number, and an OFDM symbol index number. An indexnumber of a CSI-RS may be a natural code, or may be represented by usingat least one of the following: a frame index number, a subframe indexnumber, a slot index number, an OFDM symbol index number, a CSI-RSresource index number, and a CSI-RS port index number.

S512: The terminal device reports index information of a periodic sweepsignal to the network device.

When the network device performs beam sweeping, the terminal devicereceives, by using at least one receive beam, periodic sweep signalssent by the network device, and measures received signal strengths, forexample, reference signal received power (reference signal receivedpower, RSRP for short), of these periodic sweep signals. When detectingthat a received signal strength of a periodic sweep signal is greaterthan or equal to a preset threshold, the terminal device reports anindex number of the periodic sweep signal to the network device, andrecords a receive beam that is used by the terminal device to receivethe periodic sweep signal. The receive beam and a periodic sweep beamthat corresponds to the reported periodic sweep signal form a beam pairthat can be used for communication. The index information, of theperiodic sweep signal, reported by the terminal device to the networkdevice may include index numbers of a plurality of periodic sweepsignals.

For example, it is assumed that the network device in FIG. 2 sends fourperiodic sweep signals to the terminal device 1 in a sweep period byusing the transmit beams B1 to B4. Index numbers of the four periodicsweep signals are 1, 2, 3, and 4. The terminal device uses the receivebeam A1 to receive the four periodic sweep signals. In addition, whenthe terminal device detects that received signal strengths of a periodicsweep signal 2 and a periodic sweep signal 3 are greater than or equalto a preset threshold, the terminal device reports the periodic sweepsignal 2 and the periodic sweep signal 3 to the network device, andrecords the receive beam A1. In this case, the network device and theterminal device establish a beam pair set that can be used forcommunication and that includes a beam pair B2 and A1 and a beam pair B3and A1.

S52: The network device allocates, to the terminal device, a requestsequence used to indicate a beam recovery request.

This step may take place at any moment before the terminal deviceinitiates the beam recovery request. The network device allocates aUE-specific (UE-Specific) request sequence to the terminal device.Request sequences of different terminal devices are orthogonal. Thenetwork device can learn, based on a received request sequence, whichterminal device initiates the beam recovery request. Alternatively, thenetwork device allocates a request sequence to the terminal device, andfurther allocates a UE-specific time-frequency resource to the terminaldevice. The request sequence may not be specific to the terminal device.A plurality of terminal devices may share one request sequence. Thenetwork device learns, based on the time-frequency resource on which therequest sequence is received, which terminal device initiates the beamrecovery request. Alternatively, the network device may allocate aUE-specific request sequence and a UE-specific time-frequency resourceto the terminal device.

S53: The network device and the terminal device perform beam adjustment.

After the beam pair set that can be used for communication isestablished, the network device may dynamically select some beam pairsin the beam pair set as serving beam pairs, and use other beam pairs asalternative beam pairs. The serving beam pair is a beam pair that iscurrently used for control signal transmission or data signaltransmission between the network device and the terminal device. Thealternative beam pair is a beam pair that is currently not used forcontrol signal transmission or data signal transmission.

After establishing the beam pair set that can be used for communication,the network device and the terminal device adjust at least one beam pair(including a serving beam pair and an alternative beam pair) in the beampair set, to track a channel change caused by movement or rotation ofthe terminal device or caused by an environment change. Beam adjustmentmay be initiated by the network device, or may be initiated by theterminal device proactively. This is not limited in this embodiment ofthis application.

The network device and the terminal device may perform beam adjustmentby performing the following steps:

S531: The network device sends K reference signals respectively by usingK periodic sweep beams.

The network device sends the K reference signals respectively by usingthe K periodic sweep beams around a periodic sweep beam (referred to asa target beam below) in a specific beam pair in the beam pair set. The Kperiodic sweep beams are a subset of the N periodic sweep beams in S511,K is a positive integer, and K≤N. However, usually, K is smaller than Nto reduce a quantity of reference signals. K<N is used as an example fordescription in this embodiment of this application. A reference signalis, for example but not limited to, a CSI-RS. The K reference signalsare different from the N periodic sweep signals in S511. Each of the Kreference signals has an index number, but the index number is differentfrom an index number of a periodic sweep beam. The terminal devicecannot determine a periodic sweep beam based on an index number of anyone of the K reference signals. It should be noted that the networkdevice indicates, to the terminal device, a target beam for adjustment.

S532: The terminal device reports index information of a referencesignal to the network device.

The terminal device receives, by using at least one receive beam, thereference signals sent by the network device, and measures receivedsignal strengths of these reference signals. When detecting that areceived signal strength of a reference signal is greater than or equalto a preset threshold, the terminal device reports an index number ofthe reference signal to the network device, and records a receive beamthat is used by the terminal device to receive the reference signal. Thereceive beam and a periodic sweep beam that corresponds to the reportedreference signal form a new beam pair, and a target beam pair in thebeam pair set is adjusted to be the new beam pair.

FIG. 7 is a schematic diagram of beam adjustment according to anembodiment of this application. As shown in FIG. 7, a beam pair set thatcan be used for communication and that is established by the networkdevice and the terminal device includes a beam pair 1 and a beam pair 2(as shown in FIG. 7(a)). The beam pair 1 includes a beam x on a networkdevice side and a beam x′ on a terminal device side. The beam pair 2includes a beam y on the network device side and a beam y′ on theterminal device side. The beams x and y on the network device side areboth periodic sweep beams. When the beam pair 2 is to be adjusted, thenetwork device may send K CSI-RSs respectively by using K periodic sweepbeams around the beam y on the network device side (as shown in FIG.7(b)). Finally, the beam pair 2 is adjusted from the original beam pairshown in FIG. 7(a) to a beam pair represented by dashed lines shown inFIG. 7(c) (as shown in FIG. 7(c)). The beam pair 2 obtained afteradjustment includes a beam z on the network device side and a beam z′ onthe terminal device side.

S54: The network device sends a notification message to the terminaldevice.

When the terminal device moves or rotates or an environment changes, theserving beam pair may be blocked, leading to a failure. When theterminal device detects that a received signal strength of a downlinksignal is less than a preset threshold, the terminal device detects abeam failure. When detecting the beam failure, the terminal deviceinitiates the beam recovery request. The terminal device initiates thebeam recovery request by sending, to the network device, the requestsequence allocated by the network device in S52. The terminal deviceuses a downlink receive beam in a beam pair in the current beam pair setas an uplink transmit beam to send the request sequence.

FIG. 8 is a schematic diagram of sending a request sequence on atime-frequency resource without beam adjustment according to anembodiment of this application. As shown in FIG. 8, a beam pair set thatcan be used for communication and that is established by the networkdevice and the terminal device includes a beam pair 1 and a beam pair 2.The beam pair 1 includes a beam x on the network device side and a beamx′ on the terminal device side. The beam pair 2 includes a beam y on thenetwork device side and a beam y′ on the terminal device side. The beamsx and y on the network device side are both periodic sweep beams. Thebeam pair 1 is a serving beam pair, and the beam pair 2 is analternative beam pair. When detecting a beam failure, the terminaldevice may send the request sequence to the network device by using thebeam x′ or y′. Correspondingly, the network device receives, by usingthe periodic sweep beam x or y, the request sequence sent by theterminal device. Because the network device needs to learn, in a timelymanner, whether each terminal device initiates a beam recovery request,the network device uses different periodic sweep beams as receive beamsto perform detection on different time-frequency resources. There is acorrespondence between a time-frequency resource used by the terminaldevice to send the request sequence and a periodic sweep beam (in otherwords, there is a correspondence between the time-frequency resourceused by the terminal device to send the request sequence and a periodicsweep signal). As shown in FIG. 8, a periodic sweep beam 1 correspondsto a time-frequency resource 1, the periodic sweep beam x corresponds toa time-frequency resource x, the periodic sweep beam y corresponds to atime-frequency resource y, and a periodic sweep beam N corresponds to atime-frequency resource N. It should be noted that each of thetime-frequency resources 1, x, y, and N may include one resource element(resource element, RE for short) or a plurality of REs.

The terminal device needs to transmit the request sequence on a correcttime-frequency resource. FIG. 8 is still used as an example. It isassumed that a transmit beam used by the terminal to send the requestsequence is the beam x′. The beam x′ on the terminal side is alignedwith the beam x on the network device side. The network device performsreception on the time-frequency resource x by using the beam x.Therefore, the network device can detect the request sequence only whenthe terminal device sends the request sequence on the time-frequencyresource x. If the terminal device sends the request sequence on a wrongtime-frequency resource, for example, the terminal device sends therequest sequence on the time-frequency resource y, a beam used by thenetwork device to receive the request sequence on the time-frequencyresource y is the beam y. However, the beam y is not aligned with thetransmit beam x′ of the terminal device. As a result, the network devicecannot receive the request sequence sent by the terminal device.Likewise, if the terminal sends the request sequence by using the beamy′, the request sequence should be sent on the time-frequency resourcey.

FIG. 9 is a schematic diagram of sending a request sequence on atime-frequency resource after beam adjustment according to an embodimentof this application. As shown in FIG. 9, a beam pair set established bythe network device and the terminal device includes a beam pair 1. Thebeam pair 1 includes a beam x on the network device side and a beam x′on the terminal device side. It is assumed that after beam adjustment,the beam pair 1 is adjusted to be a beam pair 2. The beam pair 2includes a beam y on the network device side and a beam y′ on theterminal device side. In this case, if the terminal device is toinitiate a beam recovery request on the beam y′, according to theforegoing descriptions, the terminal device needs to send the requestsequence on a time-frequency resource y corresponding to the beam y.However, as described in S531, the terminal device does not know anindex number of the beam y aligned with the beam y′, and therefore doesnot know which time-frequency resource should be used for sending therequest sequence.

Therefore, the network device needs to send the notification message tothe terminal device. The notification message includes index numbers ofall periodic sweep beams in a current beam pair set, that is, indexnumbers of periodic sweep signals sent by the network device by usingall the periodic sweep beams in the current beam pair set when thenetwork device performs periodic beam sweeping. The notification messagemay be sent periodically. After receiving the notification message, theterminal device can determine an index number of a periodic sweep beamaligned with a beam used to initiate the beam recovery request, andfurther determine a time-frequency resource corresponding to theperiodic sweep beam, so as to send the request sequence on the correcttime-frequency resource. In this way, the network device can correctlyreceive the beam recovery request initiated by the terminal device. Forexample, the current beam pair set includes the beam pair 1 and the beampair 2. The beam pair 1 includes the beam x on the network device sideand the beam x′ on the terminal device side. The beam pair 2 includesthe beam y on the network device side and the beam y′ on the terminaldevice side. The beams x and y on the network device side are bothperiodic sweep beams. In this case, the notification message includesindex numbers of the beam x and the beam y.

Alternatively, the notification message includes index numbers of allperiodic sweep beams obtained after adjustment in a current beam pairset, and an index number of an unadjusted periodic sweep beam in thecurrent beam pair set is not sent to the terminal device. Compared withsending index numbers of all periodic sweep beams, this can savedownlink signaling resources. For example, the current beam pair setincludes the beam pair 1 and the beam pair 2. The beam pair 1 includesthe beam x on the network device side and the beam x′ on the terminaldevice side. The beam pair 2 includes the beam y on the network deviceside and the beam y′ on the terminal device side. The beams x and y onthe network device side are both periodic sweep beams. In addition, thebeam pair 2 is obtained by adjusting a beam pair 3. The beam pair 3includes a beam z on the network device side and a beam z′ on theterminal device side. The beam pair 1 is unadjusted (to be specific,before previous beam adjustment, a beam pair set between the networkdevice and the terminal device includes the beam pair 1 and the beampair 3). In this case, the notification message includes only an indexnumber of the beam y.

Alternatively, the notification message includes a difference between anindex number of each periodic sweep beam in a current beam pair set andan index number of a corresponding periodic sweep beam in a notificationmessage sent last time. For example, the current beam pair set includesthe beam pair 1 and the beam pair 2. The beam pair 1 includes the beam xon the network device side and the beam x′ on the terminal device side.The beam pair 2 includes the beam y on the network device side and thebeam y′ on the terminal device side. The beams x and y on the networkdevice side are both periodic sweep beams. In addition, the beam pair 2is obtained by adjusting a beam pair 3. The beam pair 3 includes a beamz on the network device side and a beam z′ on the terminal device side.The beam pair 1 is unadjusted, and the notification message sent lasttime includes index numbers of the beam x and the beam z. In this case,the notification message includes a difference between index numbers ofthe beam x and the beam y and a difference between index numbers of thebeam y and the beam z.

Alternatively, the notification message includes a difference between anindex number of each periodic sweep beam obtained after adjustment in acurrent beam pair set and an index number of an unadjusted periodicsweep beam in a notification message sent last time. Referring to theforegoing example, in this case, the notification message includes onlya difference between index numbers of the beam y and the beam z.

Alternatively, the notification message includes indication information,and the indication information is used to indicate that each periodicsweep beam or each periodic sweep beam obtained after adjustment in acurrent beam pair set is quasi co-located (quasi co-located, QCL forshort), in regard to a parameter, in a reference signal sent during beamadjustment and one of the N periodic sweep signals. The parameter mayinclude one of the following: an average gain, an average latency, delayspread, a Doppler shift, Doppler spread, channel relevancy, a receivebeam, or an angle of arrival. For example, the current beam pair setincludes the beam pair 1 and the beam pair 2. The beam pair 1 includesthe beam x on the network device side and the beam x′ on the terminaldevice side. The beam pair 2 includes the beam y on the network deviceside and the beam y′ on the terminal device side. The beams x and y onthe network device side are both periodic sweep beams. In addition, thebeam pair 2 is obtained by adjusting a beam pair 3. The beam pair 3includes a beam z on the network device side and a beam z′ on theterminal device side. The beam pair 1 is unadjusted. In this case, theindication information may indicate that the beam y is quasi co-located,in regard to a parameter, in a reference signal sent during beamadjustment and one of the N periodic sweep signals.

S55: The terminal device initiates the beam recovery request.

After receiving the notification message sent by the network device, theterminal device sends the request sequence on the correct time-frequencyresource.

In this embodiment of this application, after beam adjustment, thenetwork device sends the notification message to the terminal device, tonotify the terminal device of an index number of a periodic sweep beamobtained after adjustment. After receiving the notification message, theterminal device can determine an index number of a periodic sweep beamaligned with a beam used to initiate the beam recovery request, andfurther determine a time-frequency resource corresponding to theperiodic sweep beam, so as to send the request sequence on the correcttime-frequency resource. In this way, the network device can correctlyreceive the beam recovery request initiated by the terminal device.

In this embodiment of this application, after the beam pair set that canbe used for communication is established in S51, to provide a highsignal gain for improving a data transmission rate, the network deviceand the terminal device may establish a plurality of second-level beampairs based on a first-level beam pair included in the beam pair set(referred to as a first-level beam pair set below), to establish asecond-level beam pair set that can be used for communication. A beam inthe first-level beam pair is a wide beam, and a beam in the second-levelbeam pair is a narrow beam. If a narrow beam is established based on awide beam, a receive/transmit angle of the narrow beam is within a rangeof a receive/transmit angle of the wide beam. For example, thereceive/transmit angle of the wide beam is 20 degrees to 40 degrees. Iffour narrow beams are established based on the wide beam,receive/transmit angles corresponding to the four narrow beams may be 20degrees to 25 degrees, 25 degrees to 30 degrees, 30 degrees to 35degrees, and 35 degrees to 40 degrees. When a range of areceive/transmit angle of a second-level beam on the network device sideis within a range of a receive/transmit angle of a first-level beam(namely, a periodic sweep beam) on the network device side, there is acorrespondence between the second-level beam and the periodic sweep beamon the network device side. In this case, there is also a correspondencebetween a second-level beam pair formed by the second-level beam on thenetwork device side and a second-level beam on the terminal device sidealigned with the second-level beam on the network device side, and acorrespondence between a first-level beam pair formed by the periodicsweep beam and a first-level beam on the terminal device side alignedwith the periodic sweep beam.

After the second-level beam pair set that can be used for communicationis established, the network device and the terminal device adjust atleast one second-level beam pair in the second-level beam pair set.Specifically, the network device sends the K reference signalsrespectively by using K second-level beams around a network device-sidebeam (referred to as a second-level target beam below) in a specificsecond-level beam pair (referred to as a second-level target beam pairbelow) in the second-level beam pair set. Then, the terminal devicefeeds back an index number of a selected reference signal, and records areceive beam that is used by the terminal device to receive thereference signal. The receive beam and a network device-side beam thatcorresponds to the reported reference signal form a new second-levelbeam pair, and the second-level target beam pair in the second-levelbeam pair set is also adjusted to be the new second-level beam pair.

It should be noted that the new second-level beam pair may deviate froma first-level beam pair corresponding to the second-level target beampair. To be specific, a range of a receive/transmit angle of asecond-level beam on the network device side in the new second beam pairis not within a range of a receive/transmit angle of a periodic beam inthe first-level beam pair corresponding to the second-level target beampair. For example, it is assumed that the first-level beam pair setincludes a first-level beam pair 1. The first-level beam pair 1 includesa first-level beam x on the network device side and a first-level beamx′ on the terminal device side. The first-level beam x on the networkdevice side is a periodic sweep beam. Based on the first-level beam pair1, a second-level beam pair 2 is established. The second-level beam pair2 includes a second-level beam x1 on the network device side and asecond-level beam x1′ on the terminal device side. In this case, thereis a correspondence between the second-level beam x1 and the periodicsweep beam x, and there is also a correspondence between thesecond-level beam pair 2 and the first-level beam pair 1. During beamadjustment, the second-level beam pair 2 is adjusted to be asecond-level beam pair 3. The second-level beam pair 3 includes asecond-level beam y1 on the network device side and a second-level beamy1′ on the terminal device side. The second-level beam pair 3 does notcorrespond to the first-level beam pair 1, but corresponds to afirst-level beam pair 4. In other words, the second-level beam pair 3deviates from the first-level beam pair 1. The first-level beam pair 4includes a first-level beam y on the network device side and afirst-level beam y′ on the terminal device side. The first-level beam yon the network device side is a periodic sweep beam. In this case, ifthe terminal device sends the request sequence, in consideration ofreliability or coverage, the request sequence needs to be sent by usingthe first-level beam (the beam y′) on the terminal side corresponding tothe second-level beam (the beam y1′) obtained after adjustment on theterminal side. However, in this case, the terminal device does not knowan index number of the periodic sweep beam y aligned with the beam y′,and therefore does not know which time-frequency resource should be usedfor sending the request sequence.

Therefore, in this embodiment of this application, if the second-levelbeam pair set that can be used for communication is established betweenthe network device and the terminal device, after beam adjustment isperformed on at least one second-level beam pair in the second-levelbeam pair set, the network device also needs to send a notificationmessage to the terminal device, to indicate an index number of aperiodic sweep beam (s) corresponding to a second-level beam obtainedafter adjustment or all second-level beams on the network device side inthe current second-level beam pair set. For a specific notificationmanner, refer to related descriptions in S54, and details are notdescribed herein again.

FIG. 10 is a schematic flowchart of a method for sending a messageaccording to an embodiment of this application. As shown in FIG. 10, themethod includes the following steps.

S101: A network device allocates a request sequence to a terminaldevice.

The network device allocates a UE-specific (UE-Specific) requestsequence to the terminal device. Request sequences of different terminaldevices are orthogonal. The network device can learn, based on thereceived request sequence, which terminal device sends the requestsequence. Alternatively, the network device allocates a UE-specifictime-frequency resource to the terminal device, and allocates a requestsequence to the terminal device. The request sequence may not bespecific to the terminal device. A plurality of terminal devices mayshare one request sequence. The network device learns, based on thetime-frequency resource on which the request sequence is received, whichterminal device sends the request sequence. Alternatively, the networkdevice may allocate a UE-specific request sequence and a UE-specifictime-frequency resource to the terminal device.

When the network device allocates a UE-specific time-frequency resource(namely, a dedicated time-frequency resource for the terminal device) tothe terminal device, the dedicated time-frequency resource may becarried on different channels, such as a physical uplink control channel(physical uplink control channel, PUCCH for short), a physical randomaccess channel (physical random access channel, PRACH for short), and achannel (PRACH-like) whose slot is the same as that of the physicalrandom access channel and whose frequency band is different from that ofthe physical random access channel.

In this step, the request sequence is not necessarily used to indicate abeam recovery request. In other words, the request sequence is notnecessarily used for requesting beam recovery.

S102: The terminal device sends the request sequence to the networkdevice.

S103: The network device sends a response message to the terminal devicein response to the received request sequence.

The response message indicates a time-frequency resource that thenetwork device allocates to the terminal device in response to therequest sequence. The time-frequency resource is used for subsequentuplink transmission.

Optionally, there is a specific probability that the network deviceincorrectly determines which terminal device sends the request sequence,and a terminal device that does not send the request sequence alsodecodes the response message after receiving the response message. Toavoid this case, the network device may scramble the response message byusing a radio network temporary identifier (radio network temporaryidentifier, RNTI for short). In this way, once detecting the RNTI afterreceiving the response message, the terminal device that does not sendthe request sequence does not decode the response message. The RNTI maybe obtained by using a preset function and at least one of the followingvariables: an index number of the request sequence, an index number of atime resource for sending the request sequence, and an index number of afrequency resource for sending the request sequence.

S104: The terminal device sends an indication message to the networkdevice.

When receiving the response message sent by the network device, theterminal device sends the indication message to the network device onthe time-frequency resource indicated in the response message. Theindication message indicates an actual function or purpose of therequest sequence sent by the terminal device in S102. For example, therequest sequence is the beam recovery request, a data schedulingrequest, or a beam adjustment request. Alternatively, the requestsequence may be reused for at least two of a beam recovery request, adata scheduling request, and a beam adjustment request. The beamrecovery request means: When the terminal device moves or rotates or anenvironment changes, a serving beam pair between the terminal device andthe network device may be blocked, leading to a failure; when theterminal device detects that a received signal strength of a downlinksignal is less than a preset threshold, the terminal device detects abeam failure, and initiates the beam recovery request. The datascheduling request is a request that is for requesting allocation of adata transmission resource and that is sent by the terminal device tothe network device when the terminal device is to send data. The beamadjustment request is a request for adjusting at least one beam pair ina beam pair set after the beam pair set that can be used forcommunication is established between the network device and the terminaldevice.

When the request sequence is used at least for requesting beam recovery,in this embodiment of this application, before S101, there is a step inwhich the terminal device detects the beam failure, to be specific, theterminal device receives a signal sent by the network device by using aserving beam and detects that a received signal strength of the signalis less than the preset threshold. When the terminal device detects thebeam failure, the terminal device may first determine whether there isan available beam pair currently. When there is an available beam paircurrently, the terminal device sends the request sequence used forrequesting beam recovery. The terminal device may receive a signal sentby the network device by using any beam. When the terminal devicedetects that a received signal strength of the signal is greater than orequal to the preset threshold, the terminal device determines that thereis an available beam pair currently, and sends an index number of thesignal to the network device. In addition, the indication message mayfurther include at least one of the following: a beam failure cause, aquantity of failed beams, a beam failure status, an index number of anavailable beam, and quality of the available beam.

When the request sequence is used at least for requesting datascheduling, the indication message further includes a buffer statusreport (buffer status report, BSR for short), to indicate an amount ofto-be-sent data of the terminal device or a quantity of requestedresources.

FIG. 11 is a schematic diagram of an indication message according to anembodiment of this application. As shown in FIG. 11, the indicationmessage may be implemented by using at least one media access controlcontrol element (media access control-control element, MAC CE forshort). One MAC CE includes eight bits, or bits of which a quantity isan integral multiple of 8. FIG. 11 shows a MAC CE 111 and a MAC CE 112.The indication message may be implemented by using the MAC CE 111. BitsS1 and S0 in the MAC CE 111 indicate a function of a request sequence.When S1 and S0 are respectively 0 and 1, it indicates that the requestsequence is used for requesting beam recovery. Correspondingly, in theMAC CE 111, bits B1 and B0 indicate a beam failure cause, bits C1 and C0indicate a quantity of failed beams, and bits D1 and D0 indicate anindex number of an available beam. The indication message may beimplemented by using the MAC CE 112. Bits S1 and S0 in the MAC CE 112indicate a function of a request sequence.

When S1 and S0 are respectively 0 and 0, it indicates that the requestsequence is used for requesting data scheduling. Correspondingly, bitsB5 to B0 in the MAC CE 112 indicate buffer status information.Alternatively, the indication message may be implemented by using boththe MAC CE 111 and the MAC CE 112. In this case, it indicates that therequest sequence is reused for requesting data scheduling and requestingbeam recovery, in other words, a terminal device simultaneouslyinitiates a data scheduling request and a beam recovery request.

In FIG. 11, alternatively, the MAC CE 111 may not include any dedicatedbits for indicating a function of a request sequence, but include onlybits for indicating a beam failure cause, a quantity of failed beams,and an index number of an available beam. Likewise, the MAC CE 112 maynot include any dedicated bits for indicating a function of a requestsequence, but include only bits for indicating buffer statusinformation. Further, when the MAC CE 111 or the MAC CE 112 does notinclude any dedicated bits for indicating the function of the requestsequence, a logical channel value in the MAC CE 111 or the MAC CE 112may be used to indicate the function of the request sequence. Forexample, when the logical channel value is 0, it indicates that therequest sequence is used for requesting beam recovery; when the logicalchannel value is not 0, it indicates that the request sequence is usedfor requesting data scheduling. Alternatively, a buffer statusinformation value in the MAC CE 111 or the MAC CE 112 may be used toindicate the function of the request sequence. For example, when thebuffer status information value is 0, it indicates that the requestsequence is used for requesting beam recovery; when the buffer statusinformation value is not 0, it indicates that the request sequence isused for requesting data scheduling.

S140′: The terminal device resends the request sequence to the networkdevice.

When the terminal device does not receive, within a preset time, theresponse message sent by the network device, the terminal device resendsthe request sequence to the network device. When a quantity of times ofsending the request sequence reaches a preset maximum quantity ofsending times, the terminal device performs one of the followingoperations: initiating a random access process, reporting a beamrecovery failure, and reporting a radio link failure.

In this embodiment of this application, after receiving the requestsequence from the terminal device, the network device allocates, to theterminal device, the time-frequency resource used for uplinktransmission. The terminal device reports the actual function of therequest sequence to the network device on the time-frequency resourceallocated by the network device. Further, the terminal device may reportboth the actual function of the request sequence and auxiliaryinformation corresponding to the actual function of the requestsequence. For example, when the actual function of the request sequenceis requesting beam recovery, the auxiliary information includes at leastone of the beam failure cause, the quantity of failed beams, the beamfailure status, the index number of the available beam, and the qualityof the available beam. When the actual function of the request sequenceis requesting data scheduling, the auxiliary information includes theBSR.

In this embodiment of this application, the request sequence sent by theterminal device to the network device is not necessarily used forrequesting beam recovery, but may be reused for requesting beamadjustment and/or requesting data scheduling. The network deviceallocates the time-frequency resource to the terminal device in responseto the request sequence. The terminal device sends the indicationmessage to the network device on the allocated time-frequency resource,and indicates the actual function of the request sequence in theindication message. The request sequence is reused for several possiblerequests, so that a large quantity of sequence resources are saved.

FIG. 12 is a schematic apparatus diagram of a network device accordingto an embodiment of this application. As shown in FIG. 12, the networkdevice 120 includes a sending unit 1200 and a receiving unit 1201. Thesending unit 1200 may be configured to perform S511, S531, and S54. Thereceiving unit 1201 may be configured to perform S512, S532, and S55.

FIG. 13 is a schematic apparatus diagram of a terminal device accordingto an embodiment of this application. As shown in FIG. 13, the terminaldevice 130 includes a sending unit 1300 and a receiving unit 1301. Thesending unit 1300 may be configured to perform S102 and S104. Thereceiving unit 1301 may be configured to perform S101 and S103.

FIG. 14 is a schematic apparatus diagram of another network deviceaccording to an embodiment of this application. As shown in FIG. 14, thenetwork device 140 includes a memory 1400, a transceiver 1401, and aprocessor 1402, and may further include a bus 1403 and at least oneantenna 1404. The memory 1400 is configured to store program codeincluding a computer operation instruction. The processor 1402 isconfigured to execute the computer operation instruction, to control thetransceiver 1401 to perform S51 to S55 shown in FIG. 5.

FIG. 15 is a schematic apparatus diagram of another terminal deviceaccording to an embodiment of this application. As shown in FIG. 15, theterminal device 150 includes a memory 1500, a transceiver 1501, and aprocessor 1502, and may further include a bus 1503 and at least oneantenna 1504. The memory 1500 is configured to store program codeincluding a computer operation instruction. The processor 1502 isconfigured to execute the computer operation instruction, to control thetransceiver 1501 to perform S101 to S104 shown in FIG. 10.

It should be understood that the foregoing transceiver may include atransmitter and a receiver. The transceiver may further include one ormore antennas. The memory may be a separate component, or may beintegrated into the processor. All or some of the foregoing componentsmay be integrated into a chip for implementation, for example, beintegrated into a baseband chip for implementation.

The apparatus in implementations of this application may be afield-programmable gate array (Field-Programmable Gate Array, FPGA), maybe an application-specific integrated circuit (Application-SpecificIntegrated Circuit, ASIC), may be a system on chip (System on Chip,SOC), may be a central processing unit (Central Processing Unit, CPU),may be a network processor (Network Processor, NP), may be a digitalsignal processing circuit (Digital Signal Processor, DSP), may be amicrocontroller (Micro Controller Unit, MCU), or may be a programmablecontroller (Programmable Logic Device, PLD) or another integrated chip.

A person of ordinary skill in the art may be aware that units andalgorithm steps in the examples described with reference to theembodiments disclosed in this specification can be implemented byelectronic hardware or a combination of computer software and electronichardware. Whether the functions are performed by hardware or softwaredepends on particular applications and design constraints of thetechnical solutions. A person skilled in the art may use differentmethods to implement the described functions for each particularapplication, but it should not be considered that the implementationgoes beyond the scope of the present invention.

It may be clearly understood by a person skilled in the art that, forthe purpose of ease and brevity of description, for detailed workingprocesses of the foregoing system, apparatus, and unit, reference may bemade to corresponding processes in the foregoing method embodiments, anddetails are not described herein again. For ease and brevity, the methodembodiments may also be cross-referenced, and details are not describedagain.

The term “a plurality of” in this specification means two or more. Theterms “first”, “second”, and the like in this specification are merelyintended to distinguish between different objects, but are not intendedto limit a sequence of the objects. For example, “a first symbol group”and “a second symbol group” are merely intended to distinguish betweendifferent symbol groups, but are not intended to limit a sequence of thesymbol groups. The term “and/or” in this specification describes only anassociation relationship for describing associated objects andrepresents that three relationships may exist. For example, A and/or Bmay represent the following three cases: Only A exists, both A and Bexist, and only B exists. In addition, the character “/” in thisspecification generally represents an “or” relationship betweenassociated objects. In a formula, the character “/” represents a“divide” relationship between associated objects. The preset thresholdsmentioned in the embodiments of this application may be a same presetthreshold, or may be different preset thresholds.

In the several embodiments provided in this application, it should beunderstood that the disclosed system, apparatus, and method may beimplemented in other manners. For example, the described apparatusembodiment is merely an example. For example, the unit division ismerely logical function division and may be other division in actualimplementation. For example, a plurality of units or components may becombined or may be integrated into another system, or some features maybe ignored or not performed. In addition, the displayed or discussedmutual couplings or direct couplings or communication connections may beimplemented by using some interfaces. The indirect couplings orcommunication connections between the apparatuses or units may beimplemented in electrical, mechanical, or other forms.

The units described as separate parts may or may not be physicallyseparate, and parts displayed as units may or may not be physical units,may be located in one position, or may be distributed on a plurality ofnetwork units. Some or all of the units may be selected depending on anactual requirement, to achieve the objectives of the solutions of theembodiments.

In addition, the functional units in the embodiments of the presentinvention may be integrated into one processing unit, or each of theunits may exist alone physically, or two or more units may be integratedinto one unit.

When the functions are implemented in a form of a software functionalunit and sold or used as an independent product, the functions may bestored in a computer readable storage medium. Based on such anunderstanding, the technical solutions of the present inventionessentially, or the part contributing to the prior art, or some of thetechnical solutions may be implemented in a form of a software product.The computer software product is stored in a storage medium, andincludes several instructions for instructing a computer device (whichmay be a personal computer, a server, a network device, or the like) toperform all or some of the steps of the methods described in theembodiments of the present invention. The foregoing storage mediumincludes any medium that can store program code, such as a USB flashdrive, a removable hard disk, a read-only memory (ROM, Read-OnlyMemory), a random access memory (RAM, Random Access Memory), a magneticdisk, or a compact disc.

All or some of the foregoing embodiments may be implemented by usingsoftware, hardware, firmware, or any combination thereof. When softwareis used for implementation, the embodiments may be implementedcompletely or partially in a form of a computer program product. Thecomputer program product includes one or more computer instructions.When the computer program instruction is loaded and executed on acomputer, the procedures or functions according to the embodiments ofthis application are all or partially generated. The computer may be ageneral-purpose computer, a special-purpose computer, a computernetwork, or another programmable apparatus. The computer instruction maybe stored in a computer-readable storage medium, or may be transmittedfrom a computer-readable storage medium to another computer-readablestorage medium. For example, the computer instruction may be transmittedfrom a website, computer, server, or data center to another website,computer, server, or data center in a wired (for example, a coaxialcable, an optical fiber, or a digital subscriber line (DSL)) or wireless(for example, infrared, radio, or microwave) manner. Thecomputer-readable storage medium may be any usable medium that can beaccessed by the computer, or a data storage device, such as a server ora data center, integrating one or more usable media. The usable mediummay be a magnetic medium (for example, a floppy disk, a hard disk, or amagnetic tape), an optical medium (for example, a DVD), a semiconductormedium (for example, a solid-state drive Solid State Disk (SSD)), or thelike.

The foregoing descriptions are merely specific implementations of thepresent invention, but are not intended to limit the protection scope ofthe present invention. Any variation or replacement readily figured outby a person skilled in the art within the technical scope disclosed inthe present invention shall fall within the protection scope of thepresent invention. Therefore, the protection scope of the presentinvention shall be subject to the protection scope of the claims.

What is claimed is:
 1. A method for receiving a beam recovery request,wherein the method is applied to a network device and comprises: sendinga first signal to a terminal device by using a first beam; receivingfirst index information sent by the terminal device, wherein the firstindex information indicates an index number of the first signal; sendinga first notification message to the terminal device based on the firstindex information, wherein the first notification message comprisessecond index information, wherein the second index information indicatesan index number of a second signal, and wherein the index number of thesecond signal corresponds to the first beam; and receiving, on atime-frequency resource corresponding to the first beam, the beamrecovery request sent by the terminal device.
 2. The method according toclaim 1, wherein before the sending a first signal to a terminal deviceby using a first beam, the method further comprises: sending the secondsignal to the terminal device by using the first beam; and receivingthird index information sent by the terminal device, wherein the thirdindex information indicates the index number of the second signal. 3.The method according to claim 1, wherein after the sending a firstnotification message to the terminal device, the method furthercomprises: sending a third signal to the terminal device by using asecond beam; receiving fourth index information sent by the terminaldevice, wherein the fourth index information indicates an index numberof the third signal; and sending a second notification message to theterminal device based on the fourth index information, wherein thesecond notification message comprises fifth index information, whereinthe fifth index information indicates a difference between an indexnumber of a fourth signal and the index number of the second signal, andwherein the index number of the fourth signal corresponds to the secondbeam.
 4. The method according to claim 1, wherein that the second indexinformation indicates an index number of a second signal comprises: thesecond index information indicates that the first signal and the secondsignal are quasi co-located.
 5. The method according to claim 3, whereinthe first signal comprises a first channel state information-referencesignal (CSI-RS), wherein the second signal comprises a second CSI-RS ora first synchronization signal block (SS block), wherein the thirdsignal comprises a third CSI-RS, and wherein the fourth signal comprisesa fourth CSI-RS or a second SS block.
 6. A method for sending a message,wherein the method is applied to a terminal device and comprises:sending a request sequence to a network device; receiving a responsemessage sent by the network device, wherein the response messageindicates a time-frequency resource that the network device allocates tothe terminal device in response to the request sequence, wherein theresponse message is scrambled by using a radio network temporaryidentifier (RNTI), and wherein the RNTI is obtained by using a presetfunction and at least one of an index number of the request sequence, anindex number of a time resource for sending the request sequence, and anindex number of a frequency resource for sending the request sequence;and sending an indication message to the network device on thetime-frequency resource, wherein the indication message indicates thatthe request sequence is used for at least one of the following:requesting beam recovery, requesting data scheduling, and requestingbeam adjustment.
 7. The method according to claim 6, wherein when therequest sequence is used at least for requesting beam recovery, theindication message further comprises at least one of the following: abeam failure cause, a quantity of failed beams, a beam failure status,an index number of an available beam, and quality of the available beam.8. The method according to claim 7, wherein the quantity of failed beamsis indicated by using a field of the quantity of failed beams, andwherein that the field of the quantity of failed beams is 00, 01, 10, or11 indicates that the quantity of failed beams is 1, 2, 3, or 4,respectively.
 9. The method according to claim 7, wherein the beamfailure status is indicated by using a field of the beam failure status,and wherein that the field of the beam failure status is 00 or 01indicates that the beam failure status is that a current serving beamfails or all serving beams fail, respectively.
 10. The method accordingto claim 6, wherein when the request sequence is used at least forrequesting beam recovery, before the sending a request sequence to anetwork device, the method further comprises: receiving a first signalsent by the network device by using a first beam; and detecting that areceived signal strength of the first signal is less than or equal to afirst preset threshold.
 11. The method according to claim 6, whereinafter the sending a request sequence to a network device, the methodfurther comprises: if the response message is not received within apreset time, resending the request sequence to the network device; andwhen a quantity of times of sending the request sequence to the networkdevice reaches a preset maximum quantity of sending times, performingone of the following: initiating a random access process, reporting abeam recovery failure, and reporting a radio link failure.
 12. A networkdevice, comprising: a transceiver; a memory, configured to store programcode comprising a computer operation instruction; and at least oneprocessor, the at least one processor configured to execute the computeroperation instruction to control the transceiver to perform thefollowing operations: receiving first index information sent by aterminal device, wherein the first index information indicates an indexnumber of a first signal; sending a first notification message to theterminal device based on the first index information, wherein the firstnotification message comprises second index information, wherein thesecond index information indicates an index number of a second signal,and wherein the index number of the second signal corresponds to a firstbeam; and receiving, on a time-frequency resource corresponding to thefirst beam, a beam recovery request sent by the terminal device.
 13. Thenetwork device according to claim 12, wherein the at least one processoris further configured to control the transceiver to perform thefollowing operations: sending the second signal to the terminal deviceby using the first beam; and receiving third index information sent bythe terminal device, wherein the third index information indicates theindex number of the second signal.
 14. The network device according toclaim 12, wherein the at least one processor is further configured tocontrol the transceiver to perform the following operations: sending athird signal to the terminal device by using a second beam; receivingfourth index information sent by the terminal device, wherein the fourthindex information indicates an index number of the third signal; andsending a second notification message to the terminal device based onthe fourth index information, wherein the second notification messagecomprises fifth index information, wherein the fifth index informationindicates a difference between an index number of a fourth signal andthe index number of the second signal, and wherein the index number ofthe fourth signal corresponds to the second beam.
 15. A terminal device,comprising: a transceiver; a memory, configured to store program codecomprising a computer operation instruction; and at least one processor,the at least one processor configured to execute the computer operationinstruction to control the transceiver to perform the followingoperations: sending a request sequence to a network device; receiving aresponse message sent by the network device, wherein the responsemessage indicates a time-frequency resource that the network deviceallocates to the terminal device in response to the request sequence,wherein the response message is scrambled by using a radio networktemporary identifier (RNTI), and wherein the RNTI is obtained by using apreset function and at least one of an index number of the requestsequence, an index number of a time resource for sending the requestsequence, and an index number of a frequency resource for sending therequest sequence; and sending an indication message to the networkdevice on the time-frequency resource, wherein the indication messageindicates that the request sequence is used for at least one of thefollowing: requesting beam recovery, requesting data scheduling, andrequesting beam adjustment.
 16. The terminal device according to claim15, wherein when the request sequence is used at least for requestingbeam recovery, the indication message further comprises at least one ofthe following: a beam failure cause, a quantity of failed beams, a beamfailure status, an index number of an available beam, and quality of theavailable beam.
 17. The terminal device according to claim 15, whereinwhen the request sequence is used at least for requesting beam recovery,the at least one processor is further configured to control thetransceiver to perform the following operations: receiving a firstsignal sent by the network device by using a first beam; and detectingthat a received signal strength of the first signal is less than orequal to a first preset threshold.
 18. The terminal device according toclaim 15, wherein the at least one processor is further configured tocontrol the transceiver to perform the following operations: if theresponse message is not received within a preset time, resending therequest sequence to the network device; and when a quantity of times ofsending the request sequence to the network device reaches a presetmaximum quantity of sending times, performing one of the following:initiating a random access process, reporting a beam recovery failure,and reporting a radio link failure.